Low level laser therapy (LLLT) has been used for inflammation treatment. Here, we evaluate the effect of different
doses, using continuous (830 and 980 nm) and pulsed illumination (830 nm), in the treatment of inflammation induced in
the gastrocnemius muscle of Wistar rats, through cytokines concentration in systemic blood and histological analysis of
muscle tissue. Animals were randomly divided into five groups per wavelength (5 animals per group: 10, 20, 30, 40 and
50 mW) plus a control group. LLLT was applied during five days, with constant exposure time and irradiated area (3
minutes; 0.5026 cm2). Blood was collected on days 0, 3 and 6. TNF-α, IL-1β, IL-2 and IL-6 cytokines were quantified
by ELISA. Rats were killed on day 6. Muscle inflammatory cells were counted using optical microscopy. Treatment
effects occurred for all applied doses (largest effect at 40 mW: 7.2 J, 14 J/cm2 per irradiation), with reduction of proinflammatory
TNF-α, IL-1β and IL-6 cytokines and lower number of inflammatory cells. Results were better for 830 nm.
Identical methodology was used with pulsed illumination. Average power (40 mW) and duty cycle were kept constant
(80%) at five frequencies (5, 25, 50, 100 and 200 Hz). Treatment effects were observed at higher frequencies, with no
significant differences between them. However, the treatment effect was lower than for continuous illumination. LLLT
effect on inflammation treatment can be monitored by measuring systemic blood cytokines. A larger treatment effect was
observed with continuous illumination, where results seem to be compatible with a biphasic dose response.